Devices for controlling the rate of flow of a fluid, primarily liquids, at varying line pressures, are utilized in a variety of applications, such as clothes washers and dishwashers, showers, faucets and plumbing valves, drinking fountains, ice makers, water softeners, automotive heating systems, fuel systems, water cooled equipment and heat exchangers, gas valves, pneumatic machine tools, respiratory controls, and drip irrigation and water sprinklers.
Perhaps the most effective control for this wide variety of installations is a rubber flow control washer, which can be routinely engineered to maintain a constant flow rate despite variations in line pressure. For example, various rubber flow control washers are available for maintaining an essentially constant flow in a range of from less than 1 gpm to flows in excess of 100 gpm under pressure variations ranging from 15 psi to 150 psi.
Regardless of the specific application, generally a flow control washer is designed by specifying a rubber or rubber-like material having a requisite modulus of elasticity, thickness, diameter, contour and flow aperture to give the desired quantity of flow over a range of pressures likely to be encountered in the specific application for which the flow control has been designed.
While conventional flow control washers have proven efficient for a wide variety of applications, as noted above, each washer, as also indicated above, is designed for a specific rate of flow desired, but if it is necessary to operate at a different flow rate, the flow control washer must be exchanged for another washer designed to operate at that different flow rate.
It should also be noted that there is a class of valves which incorporate an apertured rubber or rubber-like member received between two relatively rigid members that can be advanced toward and retracted away from each other to squeeze and release the rubber part to change the diameter of the opening through it. For example, U.S. Pat. Nos. 1,657,663; 3,072,151; 3,095,175; and 3,833,019 each show constructions of this general type in which an attempt is made to control flow by changing the diameter of the orifice through a resilient valve element.
It should be noted, however, that devices of this type merely adjust the flow rate for a given line pressure, but fail to provide for pressure variations that may occur, so that if pressure increases with a device of this type, the flow rate will also increase, and conversely, should the line pressure decrease the flow rate will decrease.
In the particular applications shown in the above-noted patents, flow control under varying line pressure may not be of sufficient importance to warrant a control responsive to pressure variations. For example, U.S. Pat. No. 1,657,663 discloses a device adapted to control the flow of a lime emulsion or solution used for flotation in minerals separating apparatus, U.S. Pat. Nos. 3,072,151 and 3,095,175 are directed to devices for use in butane or propane lighters, and U.S. Pat. No. 3,833,019 covers a quick-connect fitting for a trickle type irrigation system.
In many instances, however, it is desirable to not only provide fluid flow control, that is, to provide a substantially constant flow rate despite variations in line pressure, but also to be able to fix the value of that flow rate at different amounts to satisfy changed conditions. While all of the prior art discussed above either provides flow control in response to pressure variations, or a variable flow rate without regard to changes in line pressure, none of the prior art would appear to provide both flow control in response to changes in line pressure and a capability of changing the nominal value at which the flow rate is maintained.